The invention relates generally to rolls and, more particularly, to an improved sealing arrangement for hydraulically supported rolls.
Such rolls typically comprise a rotatable hollow roll forming a working roll circumference and a stationary crosshead extending lengthwise through the hollow roll to form an annular clearance space therewith. The crosshead has ends protruding from the hollow roll to which external forces can be applied for supporting the roll. Circumferentially spaced longitudinal seals are attached to the crosshead to abut the inner circumference of the hollow roll. Axially spaced transverse end seals having a generally semi-annular configuration are engaged in respective circumferential slots of the crosshead such that the transverse end seals are secured in the circumferential slots against rotation and are displaceable in the action plane of roll. The longitudinal and transverse end seals define at least one longitudinal chamber formed in the annular clearance space.
In such hydraulically supported rolls, the force generating the line pressure in the roll gap is transferred to the inner circumference of the rotating hollow roll. The circumference of longitudinal chamber is sealed by the longitudinal seals and the ends of the chamber are sealed by the transverse end seals, thereby forming a largely closed pressure space. The transverse end seals are located at the ends of the hollow roll to enable the line pressure to act along the longitudinal extent of the hollow roll. The transverse end seals pose no major problems if the bearings rotatably supporting the roll are located between the hollow roll, itself, and the crosshead, as is disclosed in German Patent No. 2025777. These bearings are arranged directly adjacent the transverse end seals and act to center the crosshead within the hollow roll to minimize the radial displacement of the transverse end seal and its countersurface.
Although the transverse end seals are fixed in position at the ends of the hollow roll in rolls of the type discussed above, there also are rolls in which the bearings are axially spaced at some distance outside the end cross seals, as is disclosed in German patent document No. 3608374, which may result in deflection of the end seals. In other rolls, the crosshead can be radially displaced in a guide relative to the hollow roll, such as is disclosed in German patent document No. 22524392 which shows a roll having a different hollow roll support arrangement. In rolls with this type of support arrangement, there is no centering action provided by the bearings. Thus, in the vicinity of the transverse end seals, considerable radial displacements between the crosshead and the hollow roll occur. These displacements can have an adverse effect on the operation of a transverse end seal. These effects include power losses due to the pressure liquid flowing out of leakage points of the transverse end seal. The leaks may be so extensive that the required high operating pressures can no longer be achieved.
Another problem arising from leaking transverse end seals occurs in rolls using a high temperature thermal oil for the pressure liquid and a separate lubricating oil for the bearings, which oils must be maintained separate and not intermixed. Reliable transverse end seals are necessary in rolls experiencing relative radial displacements between the crosshead and the hollow roll, whether by design or by virtue of bearings permitting deflection of the crosshead in the hollow roll, to prevent the undesirable mixing of oils, as well as to prevent power losses and the like.